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Date: Thu, 9 Jul 2026 08:13:49 +0200
From: Christoph Hellwig <hch@lst.de>
To: Yu Kuai <yukuai@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
	Sagi Grimberg <sagi@grimberg.me>, Alasdair Kergon <agk@redhat.com>,
	Benjamin Marzinski <bmarzins@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	Dongsheng Yang <dongsheng.yang@linux.dev>,
	Zheng Gu <cengku@gmail.com>, Coly Li <colyli@fygo.io>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Josef Bacik <josef@toxicpanda.com>, Yu Kuai <yukuai@fygo.io>,
	Nilay Shroff <nilay@linux.ibm.com>, linux-block@vger.kernel.org,
	cgroups@vger.kernel.org, linux-nvme@lists.infradead.org,
	dm-devel@lists.linux.dev, linux-bcache@vger.kernel.org
Subject: Re: [RFC PATCH v1 06/17] blk-cgroup: support non-blocking bio
 association
Message-ID: <20260709061349.GD16504@lst.de>
References: <20260704195124.1375075-1-yukuai@kernel.org> <20260704195124.1375075-7-yukuai@kernel.org>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Sun, Jul 05, 2026 at 03:51:13AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai@fygo.io>
> 
> Allow bio association helpers to be called from non-blocking paths by
> returning whether the association succeeded and by taking a nowait argument.
> The normal callers pass nowait=false and keep the existing behavior of
> creating missing blkgs.
> 
> For nowait=true, the helper only succeeds when the needed blkg already
> exists.  This lets callers set or clone a bio's bdev without entering the
> sleepable missing-blkg creation path.

I think this is not needed once we kill nonblocking bio allocations,
but if not please have a clearly visible separate API for the
non-blocking version.